INTERLACING

One of the fundamental differences in how TV sets and computer monitors generate their images is the fact that standard TVs use interlaced images and computer monitors do not.

TVs generate an image by an electron beam that "draws" horizontal lines from left to right and top to bottom. However, these lines are not drawn one after another, but rather in two passes. In one pass the odd numbered lines 1, 3, 5, and so on are drawn; in the second pass, the even line numbers 2, 4, 6, and so on are drawn. This method, which divides the image into two separate "fields," is called interlacing. NTSC TVs display almost 30 frames per second, and thus have to create almost 60 fields per second.

Interlacing is one of these aspects in video technology resulting from TV's backward compatibility discussed earlier. Newer TVs could do perfectly without interlacing, but for old TV sets, it is the only way to refresh the screen 30 times a second without producing negative display effects such as strobing.

Computer-generated images are not made up of interlaced fields. Each frame is one solid image. When rendered by video editing software however, the formerly solid image will be broken up into two fields of alternating lines.

This has consequences especially for computer graphics with very fine horizontal lines or detailed structures. The result is often interlace flicker or moiré patterns. These display artifacts can be reduced or sometimes even eliminated in post production by applying blur filters in programs like After Effects, but it takes time to figure out the right balance and render everything frame by frame. It is better to plan ahead and experiment on single frames in preproduction. Use thick lines and make also sure to check the anti-aliasing option (smoothing) in the Export Settings when possible. This will take care of many interlacing problems right from the start.

Colors

More so than other television formats, like the European PAL or the new HDTV, NTSC has a specific problem in displaying colors. That's why many people refer to the NTSC acronym often as "Never Twice the Same Color."

In terms of technology solutions and workflow while preparing your Flash files, getting your colors TV-ready is probably one of the easier aspects of Flash to TV conversion. As with almost every other aspect in this list, it is better done in pre-production, so begin working with TV safe colors rather than changing them afterward.

Although color correction is fairly easily done with decent nonlinear editing systems (NLE) or the right plug-ins, the color palette should be developed and tested early on so that there won't be too many surprises at the end of the project. The quickest way to experiment with TV display is to buy an NTSC output card for your computer and connect an average consumer television as a monitor. That way you get instant feedback on your color choices.

If you don't have NTSC output, you can use several tools to create a NTSC-safe color palette. Microsoft's color picker (http://developer.msntv.com/tools/colorpick/Default.htm), for example, is an online tool that emulates how computer colors will look on a TV screen.

A variety of programs help render colors as NTSC safe colors. Photoshop provides such an option. It's possible to open a raster graphic with the Flash movie's color palette in Photoshop and then make it NTSC color safe. This graphic can then be imported back into Flash and vectorized to get a TV-safe color palette. This should be done prior to creating the entire Flash movie. It will not work for gradients or transparent colors.

Here are a few guidelines on how to achieve NTSC-friendly color schemes:

• A quick way to get close to color safe values is to avoid RGB component values above 240. Highly intense red, green, or blue displays poorly.

• Pure white doesn't display well on television for technical reasons. It may be the web's favorite background color, but TV viewers prefer darker colors anyway.

• Don't use heavily contrasting colors next to each other in a design. They "buzz" and overlap on display. Use transitional colors between contrasting colors to soften the effect.

Because colors are so immensely important for the aesthetic success of your content, it can be quite a challenge to find the right colors and color combinations, especially when your content needs to look good on both the web and on TV.

TV-Specific Viewing Habits and Aesthetics

To these objective technical issues, you have to add the human element of viewing habits and aesthetics that TV has developed in its over 50 years of existence as a mass medium. TV's success as the world's most important information and entertainment medium, relies very much on the fact that technologically speaking, everything is pretty much geared toward the lowest common denominator. So is the content, TV critics might add, but the fact remains that everyone can participate until the screen is busted. No upgrading of hardware, no downloading of plug-ins is necessary to view the latest episode of The Simpsons.

Designing for the lowest common denominator is not always obvious for Flash designers who very often disdainfully ignore users with low bandwidth and slow processors. It's possible to get away with that attitude on the web because in computer culture people are used to technical difficulties and slow downloads. Users are much more likely to blame themselves or their equipment than the creator of the poorly functioning content.

In TV it's fundamentally different. Viewers simply don't recalibrate their sets from show to show even if you tell them to. So if the colors are off or type can't be read because it blurs, it's your fault. If you are creating content to be shown on TV sets, don't calibrate it for the highquality studio monitors that you might be working with at the post-production facility. Many things will look great on high-definition equipment and will still be far from optimal on a regular consumer set. Test your Flash-generated output thoroughly and make the cheap consumer TV your ultimate aesthetic benchmark. If everything displays well there, you're on the right track. As with a lot of things, common sense and design experience will get you far in transferring content to TV, even before video technicians apply their waveform monitors.